In a drawing process such as lithography using a charged particle beam, there have been some cases where a resist applied to a surface of a work piece is charged due to irradiation of the charged particle beam, and a trajectory of the charged particle beam is distorted due to charging, so that an error occurs in an irradiation position. This has led to a decrease in a positional accuracy of a drawing pattern formed on the work piece.
In order to suppress such an error, for example, disclosed is a technique for: estimating a charge distribution of a work piece from a drawing pattern; defining a convolution integration between the charge distribution and a response function that is an amount of deviation of a pattern with respect to a single unit charging amount as an error amount of an irradiation position; and calculating a correction amount of the irradiation position from the error amount (e.g. Patent Document 1).
However, according to electromagnetism, a superposition principle is satisfied with respect to an electric field or a potential, but the superposition principle is not satisfied with respect to a spatial position function for a charged particle. Accordingly, there are some cases where an accurate result may not be obtained from a calculation of the error amount using the above-described convolution integration between the charge distribution and the response function.
In addition, another method may be considered, in which a trajectory of a charged particle beam is calculated based on an estimated charge distribution according to electromagnetism and a correction amount of an irradiation position and an error amount of the irradiation position are calculated. However, in this case, as the charged particle beam approaches the charged position of a work piece, the strength of an electric field is close to infinity and it is impossible to perform a calculation due to excessive performance required of a computer, accordingly. In this manner, there has been a problem in that it is impossible to calculate the error amount or the correction amount at the charged position.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2007-324175